In wireless communication systems, the downlink reference signals are used to provide reference for channel estimation in coherent demodulation as well as reference for channel quality measurement in multi-user scheduling. In the LTE Rel-8 specification, one type of downlink reference format called “cell-specific reference signal” (CRS) is defined for both channel estimation and channel quality measurement. The characteristics of the LTE Rel-8 CRS is that, regardless of the multiple input multiple output (MIMO) channel rank that a mobile station actually needs, the base station always broadcasts the CRS to all the mobile stations based on the largest number of MIMO layers/ports. There is a potential problem with this approach in the development of LTE Rel-10 (also called LTE-advance or LTE-A). Due to the large number of antenna ports (up to 8) supported by LTE-A, the overhead for maintaining the Rel-8 CRS on all ports would be too high.